Affiliation: | a School of Computer and Media Sciences, The Interdisciplinary Center, P.O. Box 167, 46150, Herzliya, Israel;b Department of Computer Science, California State University, 18111 Nordhoff Street, Northridge, CA 91330-8295, USA;c Department of Mathematics, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands;d Institut für Mathematik, Technische Universität Graz, Steyrergasse 30, A-8010, Graz, Austria |